DSD - Lagan Weir Operational Staff

Tender description

Background Information The tidal river Lagan extends from Stranmillis Weir downstream for some 4.8km to a line 5m on the seaward side of the cross harbour M3 Motorway Bridge at the interface with Belfast Harbour. Management of the river centres on the successful operation of the Lagan Weir at Donegal Quay. The Lagan Weir is a dynamic structure consisting of 5 steel flap gates each 20m wide and 5m high that may be raised or lowered by individual hydraulic rams, normally under automatic control, in response to changing tidal conditions. The primary function of the weir is to retain an adequate depth of water upstream as far as Stranmillis Weir during periods of low tides to ensure that unsightly mud flats remain covered and the river may be used for recreational, sporting and amenity activities. The weir is also used as a tidal barrage during high spring tides when the gates are raised to provide flood protection to vulnerable areas of Belfast. Other features of the weir include low level drainage pipes controlled by penstocks that may be used to draw of poor quality water from the river bed, two fish passes for migratory fish and navigation signage controlling boat movements across the weir. A footbridge across the weir provides an important pedestrian linkage from Donegal Quay to Queen’s Quay. The Northern Ireland Environment Agency has set minimum standards for the quality of water in the tidal Lagan and this is monitored on a regular basis. An aeration system has been installed in the river between Stranmillis and Ravenhill Reach. Compressed air is pumped into the water through diffusers lying on the river bed to raise the level of dissolved oxygen. The river is used on a regular basis by rowers from 9 active rowing clubs. Lagan Water Sports Centre offers training in a number of water based activities. Lagan Boat Company operates a tourist cruise boat from the Lagan Weir as far as Stranmillis. Belfast Splash tours operate an amphibious Duck